Lycospidine A (1), the first example of a Lycopodium alkaloid which contains an unprecedented five-membered A ring, was Isolated from Lycopodium complanatum. The unique five-membered A ring in 1 indicates that carbons 2-5 in 1 are presumably derived from proline Instead of the lysine biosynthetically, which suggests that 1 represent a new class of Lycopodium alkaloid. In addition, the unique structural feature and biosynthetic origin of 1 shed new insight into the structural diversity of Lycopodium alkaloid analogue libraries potentially accessible by engineered biosynthesis.